Protagoras

"Πάντων χρημάτων μέτρον ἄνθρωπον εἶναι, τῶν μὲν ὄντων, ὡς ἔστι, τῶν δὲ μὴ ὄντων, ὡς οὐκ ἔστιν."

"Δύο λόγους εἶναι περὶ παντὸς πράγματος."

"Περὶ μὲν θεῶν οὐκ ἔχω εἰδέναι οὔθ᾽ ὡς εἰσίν, οὔθ᾽ ὡς οὐκ εἰσίν· πολλὰ γὰρ τὰ κωλύοντα εἰδέναι, ἥ τ᾿ ἀδηλότης καὶ βραχὺς ὢν ὁ βίος τοῦ ἀνθρώπου."

"When they [the Athenians] meet for a consultation on civic art, where they should be guided throughout by justice and good sense, they naturally allow advice from everybody, since it is held that everyone should partake of this excellence, or else that states cannot be."

"You, Socrates, began by saying that virtue can't be taught, and now you are insisting on the opposite, trying to show that all things are knowledge, justice, soundness of mind, even courage, from which it would follow that virtue most certainly can be taught."

"Der Mensch ist das Maß aller Dinge. Derjenigen, die sind, so wie sie sind. Derjenigen, die nicht sind, so wie sie nicht sind."